The filter would like to fall through the holder as its actual size is smaller than required. The previous filter was a real 20X20X4 not an 'actual size' as shown on your filter. Pleats were not even. Many actually touched each other. How does the air go through.
Okay, the price is right, however you get what you pay for. The cardboard framework is thin and flimsy and not a full 4 inches thick. They claim MERV 13, but the medium is not thick and fuzzy like Honeywell. Next time I'll spend the money and get Honeywell or similar.
The filter works great! After a February install, within two days of use, my asthma was greatly relieved (less dust/mold spores) and hubby, with COPD, was noticeably using his inhalers less often. Later, while the California wildfires were raging, we ran just the A/C fan and kept the house, inside, an ashless oasis. (Outside, the solar panels output had diminished by half from the ash fallout, before they were cleaned.)I couldnt believe how quickly the difference was felt with the inside air quality, after this filter was installed - and what a lung-saver during the worst of the fires!